If someone is simultaneously watching a user’s traffic as it enters and leaves the network, it is possible to de-anonymise the communication. This could occur if the first and last node for a connection is controlled by the same person. Tor takes some steps to avoid this possibility e.g. no two computers on the same /16 network may be chosen for each connection. However, someone with access to several networks could circumvent this measure.

Not only is route selection critical for security, but it’s also a significant performance factor. Tor nodes vary dramatically in their capacity, mainly due to their network connections. If all nodes were chosen with equal likelihood, the slower ones would cripple the network. This is why Tor weights the selection probability for a node proportional to its contribution to the network bandwidth.

Because of the dual importance of route selection, there are a number of proposals which offer an alternative to Tor’s bandwidth-weighted algorithm. Later this week at PETS I’ll be presenting my paper, co-authored with Robert N.M. Watson, “Metrics for security and performance in low-latency anonymity systems”. In this paper, we examine several route selection algorithms and evaluate their security and performance.

Intuitively, a route selection algorithm which weights all nodes equally appears the most secure because an attacker can’t make their node count any more than the others. This has been formalized by two measures: Gini coefficient and entropy. In fact the reality is more complex — uniform node selection resists attackers with lots of bandwidth, whereas bandwidth-weighting is better against attackers with lots of nodes.

Our paper explores the probability of path compromise of different route selection algorithms, when under attack by a range of different adversaries. We find that none of the proposals are optimal against all adversaries, and so summarizing effective security in terms of a single figure is not feasible. We also model the performance of the schemes and show that bandwidth-weighting offers both low latency and high resistance to attack by bandwidth-constrained adversaries.

Childs created a password that granted him exclusive access to the system, authorities said. He initially gave pass codes to police, but they didn't work. When pressed, Childs refused to divulge the real code even when threatened with arrest, they said. He was taken into custody Sunday. City officials said late Monday that they had made some headway into cracking his pass codes and regaining access to the system. Childs has worked for the city for about five years. One official with knowledge of the case said he had been disciplined on the job in recent months for poor performance and that his supervisors had tried to fire him. "They weren't able to do it - this was kind of his insurance policy," said the official, speaking on condition of anonymity because the attempted firing was a personnel matter. Authorities say Childs began tampering with the computer system June 20. The damage is still being assessed, but authorities say undoing his denial of access to other system administrators could cost millions of dollars.

So, they played three monkeys and said, “la la la, I can’t see it. la la la” (not an exact quote) But, that’s not where the absurdity ends. The EPA could have sent a printed copy and that would have been the end of it.

Nope.

Instead they rewrote the conclusions to make more palatable for the dunking bird-set. Email has always been a best effort tool that has morphed into business critical function over the years. But, to say they wouldn’t open an email…wow. Remember folks, if you are a Republican or Democrat be sure to VOTE. You have a responsibility.

From NY Times:

Over the past five days, the officials said, the White House successfully put pressure on the E.P.A. to eliminate large sections of the original analysis that supported regulation, including a finding that tough regulation of motor vehicle emissions could produce $500 billion to $2 trillion in economic benefits over the next 32 years. The officials spoke on condition of anonymity because they were not authorized to discuss the matter.

Both documents, as prepared by the E.P.A., “showed that the Clean Air Act can work for certain sectors of the economy, to reduce greenhouse gases,” one of the senior E.P.A. officials said. “That’s not what the administration wants to show. They want to show that the Clean Air Act can’t work.”

November can’t come soon enough.

Article Link

We need to create a system that allows people to pass identity claims (sometimes a full name perhaps, but at other times just an attribute such as proof of age or citizenship). This system must also address the issues of authentication, authorization, access and audit. Finally we need a good alignment of technological, social, political and economic forces so that we make real progress. The goal is to put users in control of their computing environments, increasing security and privacy, and preserving other values that we cherish such as anonymity and freedom of speech.

In fact, I found the article to be rather upsetting. Not because of the article’s thesis that strong authentication through a national ID program would not necessarily pose a threat to privacy; but rather, because of their naive (and irresponsible) handling of the realities of the biometric authentication challenge. They gloss over the real security challenges with creating a national biometric infrastructure. Here are the two quotes that are most misleading:

• “Confusing privacy with anonymity has delayed implementation of robust, virtually tamper-proof biometric authentication to replace paper-based forms of ID that neither assure privacy nor reliably prove identity.”
• “This emerging technology makes it virtually impossible to assume someone else’s unique identity.”

The problem that the authors are glossing over is that no such technology exists today, and it is unlikely to ever exist. Now, to be fair, I am assuming that a critical success factor for any national biometric program, as described, would be that the authentication devices have to be available, and usable, anyplace paper-based IDs can be used today. This of course implies that the authenticator must be an inexpensive, commodity device, easy to purchase, maintain, and operate. Such a device would have to be even more ubiquitous than the electronic credit card machine.

The problem is that the authenticator itself may be in the possession of the attacker (Perhaps after you authenticate your legitimate purchase the clerk desires to use your identity herself…). In the history of security controls, when the attacker has unsupervised at-will physical access, the attacker wins. Here are a few examples:

• Defeated copy protection on DVDs ( more & more info)
• Cold Boot Crypto Attack on hard disk encryption (more info)
• MiFare RFID Cards (more info)
• Skimming devices attached to ATM machines to steal card and PIN data (more info)

Of course, all of these systems worked in the lab. But when a security system is widely deployed, it has to withstand an enormous amount of scrutiny, and minor flaws will be exploited. And of course, the greater the financial gain, the greater the time and energy attackers invest in trying to defeat the system. The authors of the article ignore these issues, idealistically assuming biometrics will just work.

Now, of course there are lots of examples where biometrics work very effectively. But I would propose that biometric authentication is most useful when the authentication device is physically secure and the authentication itself is supervised. The MiFare example above also demonstrates two other issues:

• The system chose not to implement a reviewed and standard cryptographic algorithm - always a bad idea
• MiFare was able to sell 1 billion cards and authenticators before the system failed

The cost of investing in a national biometric authentication program, and then having the security fail, is enormous. Can you imagine deploying a biometric authentication infrastructure to every bank, police car, restaurant, shop, etc. and then having video on YouTube of it being defeated ?

- Erik

BTW, Maybe the attacker doesn’t even need to tamper with the device -> ftp://ftp.ccc.de/pub/video/Fingerabdruck_Hack/fingerabdruck.mpg

Art of Information Security would love your feedback !

What do the Cold Boot Crypto Attack, DVD Players, and MiFare tell us about the Future of Biometrics?